1. Field of the Invention
The present invention relates to a back door opening and closing apparatus for generating a torque necessary for operating to open and close a back door by a motor in opening and closing the back door provided at a rear portion of a vehicle.
2. Related Art
In a background art, there is known a vehicle having an opening and closing member of a back door, a slide door or the like which is automatically opened and closed by driving, for example, a motor in JP-A-2003-27832 or the like shown below.
According to an automatic opening and closing apparatus of an opening and closing member for a vehicle described in JP-A-2003-27832, in opening and closing, for example, a back door, a state of opening and closing the back door is detected by detecting a rotational pulse of a motor and when the period of the rotational pulse becomes considerably smaller than a standard pulse period to constitute a pinching determining time period, the apparatus detects that pinching is brought about.
Particularly, according to the automatic opening and closing apparatus of the opening and closing member of the vehicle described in JP-A-2003-27832, in order to prevent a state of pinching a foreign matter from being erroneously recognized in opening and closing the back door, at a stage before reaching the pinching determining time period, a duty ratio which is an amount of supplying current of the motor is gradually increased until firmly determining the period of the rotational pulse. Thereby, according to the automatic opening and closing apparatus of the opening and closing member for the vehicle of the background, erroneous recognition of determining that the pinching is brought about can be prevented when pinching of the foreign matter is not brought about.
Further, it is known by the background art that a target operational speed is set depending on a position of operating the back door, and when an actual operational speed is less than the target operational speed, a value of current supplied to the motor is increased by increasing the duty ratio, the current value is compared with a previously set threshold and when the current value exceeds the threshold, it is determined that pinching of the foreign matter is brought about.
However, according to the above-described background, in the case of setting a threshold to the motor current value, when a door knob is operated to pull up by the hand of an operator in automatically operating the back door to open by the motor torque, the operational speed of the back door is increased and the current supplied to the motor is reduced in accordance therewith. Thereafter, when the operator detaches the hand from the door knob, the operational speed of the back door is reduced at the instance and therefore, the torque is generated at the motor to prevent the reduction in the operational speed and therefore, the motor current is increased.
At that occasion, according to the background art, it is necessary to rapidly increase the motor current in order to increase the motor torque and there is a case in which the motor current exceeds the threshold and it is erroneously detected that pinching of the foreign matter is brought about although pinching of the foreign matter is not brought about.